The present invention relates to transparent articles having improved abrasion resistance and to a method for producing such articles.
The architectural trend toward using more glass in commercial buildings has been enhanced by the avilability of special coated and tinted glasses which not only serve an aesthetic purpose but also are functional. The most significant advantages of the special glasses are in the area of air conditioning. Since it generally costs from three to six times more to cool a building one degree than to heat it by the same amount (depending on the amount of glass used), the use of an exterior glass which will reduce the amount of solar radiation entering a building can provide substantial savings since less air conditioning equipment is required and its operation is less costly. The special glasses are also used in other areas where low heat transmittance is required, i.e., automobile windows and oven windows.
Over the past decade the market for colored and reflective glass has grown significantly. The colored glass involved is basically of two types -- tinted and coated. Tinted glass is generally made by adding selective metals such as iron, cobalt, and nickel to the molten glass during production. This method of producing colored glass is time consuming a wasteful in that when a different color of glass is desired, a four or five-day run of glass must be discarded while the change is made and the new batch stabilized. Also, large quantities of different colors and types of glass must be inventoried. In addition, although tinted glass does reduce glare, it also absorbs heat (including solar radiation) and the absorbed heat is re-radiated from both sides of the glass. Therefore, a greater amount of heat is allowed to pass through the glass than with coated glass.
Coated or reflective glass is provided with a thin film of a reflective substance on one of its surfaces. The thin film reflects the solar radiation much more effectively than tinted glass since the glass does not adsorb the radiation. Among the materials presently employed for this purpose is chromium which can be deposited on glass sheets either by thermal deposition or by the sputter-coating technique. However, it has been found that pure chromium coatings, while used with considerable success, are not wholly satisfactory in all cases in that they are suceptible to being marred or damaged when exposed over a period of time to varying atmospheric conditions, or when subjected to repeated cleaning or rough handling. Efforts have been made to overcome this condition by overlaying the chromium film with a protective coating of a siliceous material, such as Pyrex glass, but this has not proven entirely successful.
It is therefore the primary objective of this invention to improve the abrasion resistance of sputtered coatings on glass sheets.
More particularly, it is the purpose of this invention to provide a transparent coating for glass sheets or plates, deposited thereon by sputter-coating, and which possesses greater resistance to surface abrasion than relatively pure chromium coatings.